1. Field of the Invention
This invention relates to a voice input method and apparatus which provides a reliable voice input through a microphone for recognition of voice commands even though the microphone is mounted at a distance.
2. Description of The Related Art
Various systems have been developed, employing voice recognition, to monitor and control entry into and exit from motor vehicles, elevators, and important facilities (see, for example, U.S. Pat. Nos. 4,558,298 and 4,450,545). Such systems are intended to eliminate the inconvenience of prior gate or door open/close control systems which employ keys or ID (identification) cards (e.g., necessity of carrying a key or an ID card at all times and poor operability of the key or ID card sets). Further, such systems are intended to open or close a gate (door) by recognizing a voice command (e.g., an ID number) from the speech of a person, or by identifying the person from characteristics of the input speech. Such systems based on voice recognition are very satisfactory, because each person does not need to carry his key or ID card at all times and the person can be identified with high accuracy by his voice.
For accurate voice recognition, however, a voice must be collected at a high signal-to-noise ratio without contamination of ambient noise. Conventionally, a handset type microphone or close range microphone was used to avoid possible noise contamination. Either of these microphones may collect speech at a very close position to the mouth of a speaking person and achieve a desired high S/N ratio of input speech. These microphones, however, require a person to hold them during speaking, resulting in impaired operability.
To collect only desired voice sounds, the use of soundproof walls or sharp directional microphones has been considered for cutting off ambient noise. However, soundproof walls may be very expensive and the voice input apparatus may be rendered inappropriate for many uses. When a sharp directional microphone is employed, if the directional reception sector for the microphone deviates slightly from the direction toward the speaking person's mouth, it might collect a large amount of ambient noise together with desired speech, thereby reducing the S/N ratio drastically.
As is obvious from the foregoing, the related voice input apparatus based on voice recognition technology still have many problems. Remaining unsolved, until this invention, is the problem of how a person's speech can be collected at a high S/N ratio without impairing the usefulness and operability of the voice input apparatus.